From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D88993A5428 for ; Tue, 5 May 2026 13:14:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777986900; cv=pass; b=W5nvhfrAvt6aM3htaloQ9CHmpKRJwO/3A+xm4pao7M7RfAjalACamOknGPTNxCv16UdP3vVCj7akEO4pM0xwpcWT7O6YNAYgycHiNXXBJDD85K9uaP0TJ8WivpswtVpVxLAT3AlmpKVPjFncq/Q9Xc5XhmyAhJ9E9PKeTMegUcE= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777986900; c=relaxed/simple; bh=nzCbGwFb4HznMyuHrCLZ+fiTVPB/E7XpwTLI1BfhPkY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Zi2yjeqz2yUXA1b85UuChJsppiHKwL2GM90FgiuphI8RrcPjR7VXiLGeb5PUCPsIflXhlWKUmbb4L7l97J2VynNqh/a3amSgC7oKtoCNiMKirsVfTj7Jni6W3lrZ5Tc1YkOnV0ozlfSrI1uQuV+0c3izoOA1brjnYWUyRT1MDWw= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=leandro.ribeiro@collabora.com header.b=fZjl5idM; arc=pass smtp.client-ip=136.143.188.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=leandro.ribeiro@collabora.com header.b="fZjl5idM" ARC-Seal: i=1; a=rsa-sha256; t=1777986881; cv=none; d=zohomail.com; s=zohoarc; b=Kh52UljS9IVk3YoLty3YsI1r8LK5vkNvPxIL6iB1DkORU8Smt5nUXZCvRG/FD7dBXb3qWVIP5HCgMd/n86rdT13bF9DcIEEH9HvQPgBAk5jnIxAcNYxwtrQh91u/wSORfTaHB74+EgUDkbwmhUnQy+Uf5uwL7Fj03mZrFqxZVAM= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1777986881; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=yHVnHlazVOsyMOL+GZlpXCOU1yuJjKoh6BmyS/UGtcs=; b=dr1Af98sEAm4Rbd76TjdnqeVFlkFxz3AbpdEUwNTvmzmQUzAIRlahj8jLJh9H1W/DOqb9jignh+jJkarQPPzriO5ftFqYC2A+oOk84WlM0lqNlVr5DiH5bQ1Mdv6Fkxtb0jOsu6QlOrFqG9zTSQaCp4cEDMZVSQprIaSttEBud0= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=leandro.ribeiro@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1777986881; s=zohomail; d=collabora.com; i=leandro.ribeiro@collabora.com; h=Message-ID:Date:Date:MIME-Version:Subject:Subject:To:To:Cc:Cc:References:From:From:In-Reply-To:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=yHVnHlazVOsyMOL+GZlpXCOU1yuJjKoh6BmyS/UGtcs=; b=fZjl5idMOR+uH5gwlhQA9ToxBevqa1KOGVBuk+nwjlmqzR9p8nuxoEsjI3Erruyz I35++i8z7Nn08PLX9Qk1LcCqN9+5gqX+0qiuiBOPmwmGM5sNBRv2kinF1s55/7RJ1DG fyk+87e6P5fsCcUTX9Fxovgq72y4XmTDWJIY7Bjc= Received: by mx.zohomail.com with SMTPS id 177798687946491.75887068535508; Tue, 5 May 2026 06:14:39 -0700 (PDT) Message-ID: Date: Tue, 5 May 2026 10:14:33 -0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] drm: ensure blend mode supported if alpha exposed To: Jani Nikula , dri-devel@lists.freedesktop.org Cc: airlied@gmail.com, daniels@collabora.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, pekka.paalanen@collabora.com, simona@ffwll.ch, tzimmermann@suse.de, ville.syrjala@linux.intel.com, linux-kernel@vger.kernel.org References: <20260504140630.68707-1-leandro.ribeiro@collabora.com> <20260504140630.68707-3-leandro.ribeiro@collabora.com> Content-Language: en-US From: Leandro Ribeiro In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ZohoMailClient: External On 5/5/26 4:57 AM, Jani Nikula wrote: > On Mon, 04 May 2026, Leandro Ribeiro wrote: >> Before "drm/drm_blend: allow blend mode property without PREMULTI", >> userspace would have to assume that only PREMULTI was supported by >> drivers that didn't expose the blend mode property. But now userspace >> shouldn't relly on that, as they can't count with drivers always >> supporting PREMULTI. >> >> Error out if a driver expose alpha property or pixel formats with alpha >> and does not expose the blend mode property. This way userspace don't >> have to guess. Drivers that hit such error must be fixed. >> >> Signed-off-by: Leandro Ribeiro >> --- >> drivers/gpu/drm/drm_crtc_internal.h | 1 + >> drivers/gpu/drm/drm_drv.c | 7 ++++- >> drivers/gpu/drm/drm_mode_config.c | 42 +++++++++++++++++++++++++++++ >> 3 files changed, 49 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h >> index c09409229644..bdbb6b9b94ea 100644 >> --- a/drivers/gpu/drm/drm_crtc_internal.h >> +++ b/drivers/gpu/drm/drm_crtc_internal.h >> @@ -96,6 +96,7 @@ int drm_mode_setcrtc(struct drm_device *dev, >> int drm_modeset_register_all(struct drm_device *dev); >> void drm_modeset_unregister_all(struct drm_device *dev); >> void drm_mode_config_validate(struct drm_device *dev); >> +int drm_mode_config_enforce(struct drm_device *dev); >> >> /* drm_modes.c */ >> const char *drm_get_mode_status_name(enum drm_mode_status status); >> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c >> index 985c283cf59f..76766a370650 100644 >> --- a/drivers/gpu/drm/drm_drv.c >> +++ b/drivers/gpu/drm/drm_drv.c >> @@ -1059,9 +1059,14 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags) >> const struct drm_driver *driver = dev->driver; >> int ret; >> >> - if (!driver->load) >> + if (!driver->load) { >> drm_mode_config_validate(dev); >> >> + ret = drm_mode_config_enforce(dev); > > Reading the code, I'll have no idea what "enforce" means here. Reading > the function itself isn't helping either. > > BR, > Jani. > Yes, the function name choice wasn't good. drm_mode_config_validate() only produces warnings, while drm_mode_config_enforce() returns error codes and should be used to prevent initializing a driver that does not comply with the required rules. In this case, the rule being added is supporting plane alpha but not the blend mode property. I could add such kind of rule to drm_mode_config_validate() itself, but I wasn't sure if people would be happy with it producing both warnings and errors. But maybe that would be a better approach than what I did. > >> + if (ret) >> + return ret; >> + } >> + >> WARN_ON(!dev->managed.final_kfree); >> >> if (drm_dev_needs_global_mutex(dev)) >> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c >> index 66f7dc37b597..20fd26ecb957 100644 >> --- a/drivers/gpu/drm/drm_mode_config.c >> +++ b/drivers/gpu/drm/drm_mode_config.c >> @@ -738,3 +738,45 @@ void drm_mode_config_validate(struct drm_device *dev) >> "Must have as many primary planes as there are CRTCs, but have %u primary planes and %u CRTCs", >> num_primary, dev->mode_config.num_crtc); >> } >> + >> +static int plane_require_blend_mode_for_alpha(struct drm_plane *plane) >> +{ >> + struct drm_device *dev = plane->dev; >> + const struct drm_format_info *fmt; >> + u32 i; >> + >> + /* blend mode property supported, no need to check anything */ >> + if (plane->blend_mode_property) >> + return 0; >> + >> + if (plane->alpha_property) { >> + drm_err(dev, "[PLANE:%d:%s] alpha property exposed but blend mode not setup", >> + plane->base.id, plane->name); >> + return -EINVAL; >> + } >> + >> + for (i = 0; i < plane->format_count; i++) { >> + fmt = drm_format_info(plane->format_types[i]); >> + if (fmt->has_alpha) { >> + drm_err(dev, "[PLANE:%d:%s] pixel format with alpha exposed but blend mode not setup", >> + plane->base.id, plane->name); >> + return -EINVAL; >> + } >> + } >> + >> + return 0; >> +} >> + >> +int drm_mode_config_enforce(struct drm_device *dev) >> +{ >> + struct drm_plane *plane; >> + int ret; >> + >> + drm_for_each_plane(plane, dev) { >> + ret = plane_require_blend_mode_for_alpha(plane); >> + if (ret) >> + return ret; >> + } >> + >> + return 0; >> +} > -- Leandro Ribeiro